Selecting data for storage in a dispersed storage network

ABSTRACT

A method includes receiving a first write request that includes a first encoded data slice, a slice name, a new revision level associated with the slice name, and a previous revision level associated with the slice name. The method further includes determining whether another write request from another requesting device is pending. The other write request includes another encoded data slice, the slice name, the new revision level, and the previous revision level. The method further includes when the other write request is pending, adding the first write request to a list of pending write requests for the slice name. The method further includes generating a write response to the first write request to include the list of pending write requests. The method further includes receiving a finalize request for the first or the other encoded data slice. The method further includes closing the list of pending write requests.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

Aspects of this invention relates generally to computer networks and more particularly to dispersed storage of data and distributed task processing of data.

Description of Related Art

Computing devices are known to communicate data, process data, and/or store data. Such computing devices range from wireless smart phones, laptops, tablets, computers (PCs), work stations, and video game devices, to data centers that support millions of web searches, stock trades, or on-line purchases every day. In general, a computing device includes a central processing unit (CPU), a memory system, user input/output interfaces, peripheral device interfaces, and an interconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using “cloud computing” to perform one or more computing functions (e.g., a service, an application, an algorithm, an arithmetic logic function, etc.) on behalf of the computer. Further, for large services, applications, and/or functions, cloud computing may be performed by multiple cloud computing resources in a distributed manner to improve the response time for completion of the service, application, and/or function. For example, Hadoop is an open source software framework that supports distributed applications enabling application execution by thousands of computers.

In addition to cloud computing, a computer may use “cloud storage” as part of its memory system. As is known, cloud storage enables a user, via its computer, to store files, applications, etc. on an Internet storage system. The Internet storage system may include a RAID (redundant array of independent disks) system and/or a dispersed storage system that uses an error correction scheme to encode data for storage.

Distributed storage systems are known to utilize a three-phase process for writing consistently in a dispersed storage network (DSN) memory, where the three phases include a write phase, a commit phase, and a finalize phase. The three phases address consistency issues that may arise from different storage units of the DSN holding different revisions of encoded data slices, where data is dispersed storage error encoded to produce the encoded data slices. The three phases are known to utilize a threshold approach to advance the writing process to the next phase or to reverse the process when conflicts and errors arise to maintain consistency of revision storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a distributed computing system in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing core in accordance with the present invention;

FIGS. 3-4 are schematic block diagrams of an embodiment of a dispersed storage network (DSN) in accordance with the present invention; and

FIG. 5 is a flowchart illustrating an example of selecting data for storage in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a distributed computing system 10 that includes a user device 12 and/or a user device 14, a distributed storage and/or task (DST) processing unit 16, a distributed storage and/or task network (DSTN) managing unit 18, a DST integrity processing unit 20, and a distributed storage and/or task network (DSTN) module 22. The components of the distributed computing system 10 are coupled via a network 24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN). Hereafter, the distributed computing system 10 may be interchangeably referred to as a dispersed storage network (DSN).

The DSTN module 22 includes a plurality of distributed storage and/or task (DST) execution units 36 that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.). Each of the DST execution units is operable to store dispersed error encoded data and/or to execute, in a distributed manner, one or more tasks on data. The tasks may be a simple function (e.g., a mathematical function, a logic function, an identify function, a find function, a search engine function, a replace function, etc.), a complex function (e.g., compression, human and/or computer language translation, text-to-voice conversion, voice-to-text conversion, etc.), multiple simple and/or complex functions, one or more algorithms, one or more applications, etc. Hereafter, the DST execution unit may be interchangeably referred to as a storage unit and a set of DST execution units may be interchangeably referred to as a set of storage units.

Each of the user devices 12-14, the DST processing unit 16, the DSTN managing unit 18, and the DST integrity processing unit 20 include a computing core 26 and may be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. User device 12 and DST processing unit 16 are configured to include a DST client module 34.

With respect to interfaces, each interface 30, 32, and 33 includes software and/or hardware to support one or more communication links via the network 24 indirectly and/or directly. For example, interface 30 supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network 24, etc.) between user device 14 and the DST processing unit 16. As another example, interface 32 supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network 24) between user device 12 and the DSTN module 22 and between the DST processing unit 16 and the DSTN module 22. As yet another example, interface 33 supports a communication link for each of the DSTN managing unit 18 and DST integrity processing unit 20 to the network 24.

The distributed computing system 10 is operable to support dispersed storage (DS) error encoded data storage and retrieval, to support distributed task processing on received data, and/or to support distributed task processing on stored data. In general, and with respect to DS error encoded data storage and retrieval, the distributed computing system 10 supports three primary operations: storage management, data storage and retrieval, and data storage integrity verification. In accordance with these three primary functions, data can be encoded (e.g., utilizing an information dispersal algorithm (IDA), utilizing a dispersed storage error encoding process), distributedly stored in physically different locations, and subsequently retrieved in a reliable and secure manner. Hereafter, distributedly stored may be interchangeably referred to as dispersed stored. Such a system is tolerant of a significant number of failures (e.g., up to a failure level, which may be greater than or equal to a pillar width (e.g., an IDA width of the IDA) minus a decode threshold minus one) that may result from individual storage device (e.g., DST execution unit 36) failures and/or network equipment failures without loss of data and without the need for a redundant or backup copy. Further, the distributed computing system 10 allows the data to be stored for an indefinite period of time without data loss and does so in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

The second primary function (i.e., distributed data storage and retrieval) begins and ends with a user device 12-14. For instance, if a second type of user device 14 has data 40 to store in the DSTN module 22, it sends the data 40 to the DST processing unit 16 via its interface 30. The interface 30 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). In addition, the interface 30 may attach a user identification code (ID) to the data 40.

To support storage management, the DSTN managing unit 18 performs DS management services. One such DS management service includes the DSTN managing unit 18 establishing distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for a user device 12-14 individually or as part of a group of user devices. For example, the DSTN managing unit 18 coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within memory of the DSTN module 22 for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The DSTN managing unit 18 may facilitate storage of DS error encoding parameters for each vault of a plurality of vaults by updating registry information for the distributed computing system 10. The facilitating includes storing updated system registry information in one or more of the DSTN module 22, the user device 12, the DST processing unit 16, and the DST integrity processing unit 20.

The DS error encoding parameters (e.g., or dispersed storage error coding parameters for encoding and decoding) include data segmenting information (e.g., how many segments data (e.g., a file, a group of files, a data block, etc.) is divided into), segment security information (e.g., per segment encryption, compression, integrity checksum, etc.), error coding information (e.g., pillar/IDA width, decode threshold, read threshold, write threshold, etc.), slicing information (e.g., the number of encoded data slices that will be created for each data segment); and slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

The DSTN managing unit 18 creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSTN module 22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

The DSTN managing unit 18 creates billing information for a particular user, a user group, a vault access, public vault access, etc. For instance, the DSTN managing unit 18 tracks the number of times a user accesses a non-public vault and/or public vaults, which can be used to generate a per-access billing information. In another instance, the DSTN managing unit 18 tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate a per-data-amount billing information.

Another DS management service includes the DSTN managing unit 18 performing network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, DST execution units, and/or DST processing units) from the distributed computing system 10, and/or establishing authentication credentials for DST execution units 36. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the system 10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the system 10.

To support data storage integrity verification within the distributed computing system 10, the DST integrity processing unit 20 performs rebuilding of ‘bad’ or missing encoded data slices. At a high level, the DST integrity processing unit 20 performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSTN module 22. For retrieved encoded slices, they are checked for errors due to data corruption, outdated version, etc. If a slice includes an error, it is flagged as a ‘bad’ slice. For encoded data slices that were not received and/or not listed, they are flagged as missing slices. Bad and/or missing slices are subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices to produce rebuilt slices. The rebuilt slices are stored in memory of the DSTN module 22. Note that the DST integrity processing unit 20 may be a separate unit as shown, it may be included in the DSTN module 22, it may be included in the DST processing unit 16, and/or distributed among the DST execution units 36.

Each slice name is unique to a corresponding encoded data slice and includes multiple fields associated with the overall namespace of the DSN. For example, the fields may include a pillar number/pillar index, a vault identifier, an object number uniquely associated with a particular file for storage, and a data segment identifier of a plurality of data segments, where the particular file is divided into the plurality of data segments. For example, each slice name of a set of slice names corresponding to a set of encoded data slices that has been dispersed storage error encoded from a common data segment varies only by entries of the pillar number field as each share a common vault identifier, a common object number, and a common data segment identifier.

To support distributed task processing on received data, the distributed computing system 10 has two primary operations: DST (distributed storage and/or task processing) management and DST execution on received data. With respect to the storage portion of the DST management, the DSTN managing unit 18 functions as previously described. With respect to the tasking processing of the DST management, the DSTN managing unit 18 performs distributed task processing (DTP) management services. One such DTP management service includes the DSTN managing unit 18 establishing DTP parameters (e.g., user-vault affiliation information, billing information, user-task information, etc.) for a user device 12-14 individually or as part of a group of user devices.

Another DTP management service includes the DSTN managing unit 18 performing DTP network operations, network administration (which is essentially the same as described above), and/or network maintenance (which is essentially the same as described above). Network operations include, but are not limited to, authenticating user task processing requests (e.g., valid request, valid user, etc.), authenticating results and/or partial results, establishing DTP authentication credentials for user devices, adding/deleting components (e.g., user devices, DST execution units, and/or DST processing units) from the distributed computing system, and/or establishing DTP authentication credentials for DST execution units.

To support distributed task processing on stored data, the distributed computing system 10 has two primary operations: DST (distributed storage and/or task) management and DST execution on stored data. With respect to the DST execution on stored data, if the second type of user device 14 has a task request 38 for execution by the DSTN module 22, it sends the task request 38 to the DST processing unit 16 via its interface 30. With respect to the DST management, it is substantially similar to the DST management to support distributed task processing on received data.

FIG. 2 is a schematic block diagram of an embodiment of a computing core 26 that includes a processing module 50, a memory controller 52, main memory 54, a video graphics processing unit 55, an input/output (IO) controller 56, a peripheral component interconnect (PCI) interface 58, an IO interface module 60, at least one IO device interface module 62, a read only memory (ROM) basic input output system (BIOS) 64, and one or more memory interface modules. The one or more memory interface module(s) includes one or more of a universal serial bus (USB) interface module 66, a host bus adapter (HBA) interface module 68, a network interface module 70, a flash interface module 72, a hard drive interface module 74, and a DSTN interface module 76.

The DSTN interface module 76 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). The DSTN interface module 76 and/or the network interface module 70 may function as the interface 30 of the user device 14 of FIG. 1. Further note that the IO device interface module 62 and/or the memory interface modules may be collectively or individually referred to as IO ports.

FIGS. 3-4 are schematic block diagrams of an embodiment of a dispersed storage network (DSN) that includes distributed storage and task (DST) processing units A and B, the network 24 of FIG. 1, and a set of DST execution units 1-n. Hereafter, each DST processing unit may be interchangeably referred to as a computing device of one or more computing devices of the DSN, where each computing device includes an interface, a memory, and a processing module. The interface may be implemented utilizing the interface 32 of FIG. 1. The memory may be implemented utilizing the main memory 54 of FIG. 2 and/or any other memory devices including a solid-state memory and a magnetic disk drive memory. The processing module may be implemented utilizing the processing module 50 of FIG. 2. Each DST processing unit may be implemented utilizing the DST processing unit 16 of FIG. 1.

Each DST execution unit may be implemented utilizing the DST execution unit 36 of FIG. 1 and includes the processing module 50 of FIG. 2, the main memory 54 of FIG. 2 and a memory 88. The memory 88 may be implemented utilizing one or more of solid-state memory, magnetic disk drive memory, optical disk drive memory, etc. Hereafter, each DST execution unit may be interchangeably referred to as a storage unit and the set of DST execution units may be interchangeably referred to as a set of storage units. The DSN functions to select data for storage, where a plurality of requesting devices dispersed storage error encoded data to produce a corresponding set of encoded data slices for storage in the set of DST execution units.

FIGS. 3 and 4 illustrate an example of operation of the selecting of the data for storage where, as illustrated in FIG. 3, the DST processing unit A issues a set of write requests A1-An to the set of DST execution units 1-n and the DST processing unit B issues, via the network 24, a set of write requests B1-Bn to the set of DST execution units 1-n. A storage unit receives, from a first requesting device, a first write request that includes a first encoded data slice, a slice name, a new revision level associated with the slice name, and a previous revision level associated with the slice name. For example, the DST execution unit 2 receives, from the DST processing unit A as the first requesting device, the write request A2 as the first write request, where the write request A2 includes an encoded data slice A2, a slice name of 458, a new revision level of a2, a previous revision level of 1, and a transaction identifier (ID) of A326.

Having received the first write request, the storage unit determines whether another write request from another requesting device is pending, where the other write request includes another encoded data slice, the slice name, the new revision level associated with the slice name, and the previous revision level associated with the slice name. The first write request includes a first transaction value and the other write request including a second transaction value and when the other write request is pending, a list a list of pending write requests includes an ordered list of the first and second transaction values. For example, the processing module 50 of the DST execution unit 1 indicates that the other write request from the other requesting device is not pending when the DST execution unit 1 has received the first write request from the DST processing unit A and has not yet received the other write request from the DST processing unit B. As another example, the processing module 50 of the DST execution unit 2 indicates that the other write request from the other requesting device is pending when the DST execution unit 2 has received the first write request from the DST processing unit A and after receiving the other write request from the DST processing unit B.

When the other write request is pending, the storage unit adds the first write request to the list of pending write requests for the slice name. For example, when receiving the write request A2, the processing module 50 of the DST execution unit 2 adds the write request A2 to the list of pending write requests for the slice name 458, where the list of pending write requests includes, in order, the write request B2 followed by the write request A2. Having added the first write request to the list of pending write requests, the storage unit generates a write response to the first write request, where the write response includes the list of pending write requests. For example, the processing module 50 of the DST execution unit 2 generates a write response A2 to include the list of pending write requests and sends, via the network 24, the write response A2 to the DST processing unit A in response to receiving the write request A2.

FIG. 4 further illustrates the example of operation of the selecting of the data where, having generated the write response to the first write request, the storage unit receives, in response to the write response, a finalize request to finalize storage of the first or the other encoded data slice. For example, the DST processing unit A issues a set of finalize requests A1-An to the set of DST execution units and the DST execution unit 1 receives the finalize request A 1. The storage unit determines that the finalize request is regarding the first encoded data slice when the finalize request includes the first transaction value. Alternatively, the storage unit determines that the finalize request is regarding the other encoded data slice when the finalize request includes the second transaction value. For example, the processing module 50 of the DST execution unit 1 determines that the finalize request is regarding the encoded data slice A1 when the finalize request includes the transaction value of A326 associated with the write request for the encoded data slice A1 and the processing module 50 of the DST execution unit 2 determines that the finalize request is regarding the encoded data slice A2 when the finalize request includes the transaction value of A326 associated with the write request for the encoded data slice A1.

When the finalize request is regarding the first encoded data slice, storage unit deletes the other encoded data slice. For example, the processing module 50 of the DST execution unit 2 deletes the encoded data slice B2 from the memory 88 of the DST execution unit 2. Having deleted the other encoded data slice, the storage unit deletes a previously stored encoded data slice having the slice name and the previous revision level. For example, the processing module 50 of the DST execution unit 2 deletes the revision 1 encoded data slice A2 from the memory 88 of the DST execution unit 2. Alternatively, the storage unit retains encoded data slices of one or more previous revision levels. Having deleted the previously stored encoded data slice, the storage unit updates a most current revision level to the new revision level and closes the list of pending write requests for the slice name. For example, the processing module 50 of the DST execution unit 2 updates an indicator stored in the main memory 54 that the revision level a2 is the most current revision level.

Returning to FIG. 3, when another write request is not pending (e.g., DST execution unit 1 receives the write request A1 that has not yet write request B1), the storage unit opens the list of pending write requests to include the first write request. For example, the processing module 50 of the DST execution unit 1 generates the list of pending write requests to include the write request A1 and stores the list of pending write requests in the main memory 54 of the DST execution unit 1.

Having opened the list of pending write requests, the storage unit generates the write response to the first write request, where the write response includes the list of pending write requests. For example, the processing module 50 of the DST execution unit 1 generates a write response A1 that includes the list of pending write requests which indicates that only write request A1 has been received and sends, via the network 24, the write response A1 to the DST processing unit A.

Turning again to FIG. 4, having sent the write response, the storage unit receives, in response to the write response, a first finalize request to finalize storage of the first encoded data slice. For example, the DST execution unit 1 receives the finalize request A1. Having received the finalize request, the storage unit closes the list of pending write requests for the slice name and indicates that the most current revision level is the revision level a2.

Alternatively, or in addition to, the storage unit determines, prior to receiving the first finalize request, whether the other write request is received. For example, the processing module 50 of the DST execution unit 1 determines whether the write requests B1 has been received. When the other write request is received prior to receiving the first finalize request, the storage unit updates the list of pending write requests to include the other write request. For example, the processing module 50 of the DST execution unit 1 recovers the list of pending write requests from the main memory 54 of the DST execution unit 1, and adds the write request B1 to the list of pending write requests, and stores the updated list of pending write requests in the main memory 54 of the DST execution unit 1. Having updated the list of pending write requests, the storage unit receives, in response to the write response, the finalize request to finalize storage of the first or the other encoded data slice. Having received the finalize request, the storage unit closes the list of pending write requests for the slice name.

FIG. 5 is a flowchart illustrating an example of selecting data for storage. In particular, a method is presented for use in conjunction with one or more functions and features described in conjunction with FIGS. 1-2, 3-4, and also FIG. 5. The method includes step 120 where a processing module of a storage unit of a dispersed storage network (DSN), receives from a first requesting device (e.g., a distributed storage and task (DST) processing unit), a first write request that includes a first encoded data slice, a slice name, a new revision level associated with the slice name, and a previous revision level associated with the slice name.

The method continues at step 122 where the processing module determines whether another write request from another requesting device is pending, where the other write request includes another encoded data slice, the slice name, the new revision level associated with the slice name, and the previous revision level associated with the slice name. The first write request includes a first transaction value and the other write request including a second transaction value.

A list of pending write requests includes an ordered list of the first and second transaction values. When the other write request is not pending, the method branches to step 136. When the other request is pending, the method continues to step 124.

When the other write request is pending, the processing module adds the first write request to the list of pending write requests for the slice name. The method continues at step 126 where the processing module generates a write response to the first write request, where the write response includes the list of pending write requests. The method continues at step 128 where the processing module receives, in response to the write response, a finalize request to finalize storage of the first or the other encoded data slice. The processing module determines that the finalize request is regarding the first encoded data slice when the finalize request includes the first transaction value.

When the finalize request is regarding the first encoded data slice, the method continues at step 130 where the storage unit deletes the other encoded data slice. The method continues at step 132 where the processing module deletes a previously stored encoded data slice having the slice name and the previous revision level. The method continues at step 134 where the processing module updates a most current revision level to the new revision level and closes the list of pending write requests for the slice name.

When another write request is not pending, the method continues at step 136 where the processing module opens the list of pending write requests to include the first write request. The method continues at step 138 where the processing module generates the write response to the first write request, where the write response includes the list of pending write requests. The method continues at step 140 where the processing module receives, in response to the write response, a first finalize request to finalize storage of the first encoded data slice. The method continues at step 142 where the processing module closes the list of pending write requests for the slice name.

Alternatively, the processing module determines, prior to receiving the first finalize request, whether the other write request is received. When the other write request is received prior to receiving the first finalize request, the processing module updates the list of pending write requests to include the other write request, and, in response to the write response, receives the finalize request to finalize storage of the first or the other encoded data slice, and closes the list of pending write requests for the slice name.

The method described above in conjunction with the processing module can alternatively be performed by other modules of the dispersed storage network or by other devices. For example, any combination of a first module, a second module, a third module, a fourth module, etc., of one or more computing devices may perform the method described above. In addition, at least one memory section (e.g., a first memory section, a second memory section, a third memory section, a fourth memory section, a fifth memory section, a sixth memory section, etc., of a non-transitory computer readable storage medium and/or a computer readable storage device such as a computer readable memory device) that stores operational instructions can, when executed by one or more processing modules of the one or more computing devices of the dispersed storage network (DSN), cause the one or more computing devices to perform any or all of the method steps described above.

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1.

As may also be used herein, the terms “processing module”, “processing circuit”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.

The present invention has been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.

The present invention may have also been described, at least in part, in terms of one or more embodiments. An embodiment of the present invention is used herein to illustrate the present invention, an aspect thereof, a feature thereof, a concept thereof, and/or an example thereof. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process that embodies the present invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of the various embodiments of the present invention. A module includes a processing module, a functional block, hardware, and/or software stored on memory for performing one or more functions as may be described herein. Note that, if the module is implemented via hardware, the hardware may operate independently and/or in conjunction software and/or firmware. As used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

While particular combinations of various functions and features of the present invention have been expressly described herein, other combinations of these features and functions are likewise possible. The present invention is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A method for execution by a storage unit of a dispersed storage network (DSN), the method comprises: receiving, by the storage unit, a first write request from a first requesting device, wherein the first write request includes a first encoded data slice, a slice name, a new revision level associated with the slice name, and a previous revision level associated with the slice name; determining, by the storage unit, whether another write request from another requesting device is pending, wherein the other write request includes another encoded data slice, the slice name, the new revision level associated with the slice name, and the previous revision level associated with the slice name; and when the other write request is pending: adding, by the storage unit, the first write request to a list of pending write requests for the slice name; generating, by the storage unit, a write response to the first write request, wherein the write response includes the list of pending write requests; receiving, by the storage unit, in response to the write response, a finalize request from the first requesting device to finalize storage of the first or the other encoded data slice; and closing, by the storage unit, the list of pending write requests for the slice name.
 2. The method of claim 1 further comprises: when the finalize request is regarding the first encoded data slice: deleting, by the storage unit, the other encoded data slice; and updating, by the storage unit, a most current revision level to the new revision level.
 3. The method of claim 2 further comprises: the first write request including a first transaction value; the other write request including a second transaction value; and determining, by the storage unit, that the finalize request is regarding the first encoded data slice when the finalize request includes the first transaction value.
 4. The method of claim 2 further comprises: deleting, by the storage unit, a previously stored encoded data slice having the slice name and the previous revision level.
 5. The method of claim 1 further comprises: when another write request is not pending: opening, by the storage unit, the list of pending write requests to include the first write request; generating, by the storage unit, the write response to the first write request, wherein the write response includes the list of pending write requests; receiving, by the storage unit, in response to the write response, a first finalize request to finalize storage of the first encoded data slice; and closing, by the storage unit, the list of pending write requests for the slice name.
 6. The method of claim 5 further comprises: determining, by the storage unit, prior to receiving the first finalize request, whether the other write request is received; when the other write request is received prior to receiving the first finalize request, updating, by the storage unit, the list of pending write requests to include the other write request; receiving, by the storage unit, in response to the write response, the finalize request to finalize storage of the first or the other encoded data slice; and closing, by the storage unit, the list of pending write requests for the slice name.
 7. The method of claim 1 further comprises: the first write request including a first transaction value; the other write request including a second transaction value; and the list of pending write requests includes an ordered list of the first and second transaction values.
 8. A storage unit of a dispersed storage network (DSN) comprises: an interface; memory; and a processing module operably coupled to the interface and the memory, wherein the processing module is operable to: receive, via the interface, a first write request from a first requesting device, wherein the first write request includes a first encoded data slice, a slice name, a new revision level associated with the slice name, and a previous revision level associated with the slice name; determine whether another write request from another requesting device is pending, wherein the other write request includes another encoded data slice, the slice name, the new revision level associated with the slice name, and the previous revision level associated with the slice name; and when the other write request is pending: add the first write request to a list of pending write requests for the slice name; generate a write response to the first write request, wherein the write response includes the list of pending write requests; receive, via the interface and in response to the write response, a finalize request from the first requesting device to finalize storage of the first or the other encoded data slice; and close the list of pending write requests for the slice name.
 9. The storage unit of claim 8, wherein the processing module is further operable to: when the finalize request is regarding the first encoded data slice: delete the other encoded data slice; and update a most current revision level to the new revision level.
 10. The storage unit of claim 9 further comprises: the first write request including a first transaction value; the other write request including a second transaction value; and wherein the processing module is further operable to determine that the finalize request is regarding the first encoded data slice when the finalize request includes the first transaction value.
 11. The storage unit of claim 9, wherein the processing module is further operable to: delete a previously stored encoded data slice having the slice name and the previous revision level.
 12. The storage unit of claim 8, wherein the processing module is further operable to: when another write request is not pending: open the list of pending write requests to include the first write request; generate a write response to the first write request, wherein the write response includes the list of pending write requests; receive, via the interface and in response to the write response, a first finalize request to finalize storage of the first encoded data slice; and close the list of pending write requests for the slice name.
 13. The storage unit of claim 12, wherein the processing module is further operable to: determine, prior to receiving the first finalize request, whether the other write request is received; when the other write request is received prior to receiving the first finalize request, update the list of pending write requests to include the other write request; receive, via the interface and in response to the write response, the finalize request to finalize storage of the first or the other encoded data slice; and close the list of pending write requests for the slice name.
 14. The storage unit of claim 8 further comprises: the first write request including a first transaction value; the other write request including a second transaction value; and the list of pending write requests includes an ordered list of the first and second transaction values.
 15. A computer readable storage device comprises: a first memory section that stores operational instructions that, when executed by a storage unit, causes the storage unit to: receive a first write request from a first requesting device, wherein the first write request includes a first encoded data slice, a slice name, a new revision level associated with the slice name, and a previous revision level associated with the slice name; a second memory section that stores operational instructions that, when executed by the storage unit, causes the storage unit to: determine whether another write request from another requesting device is pending, wherein the other write request includes another encoded data slice, the slice name, the new revision level associated with the slice name, and the previous revision level associated with the slice name; and a third memory section that stores operational instructions that, when executed by the storage unit, causes the storage unit to: when the other write request is pending: add the first write request to a list of pending write requests for the slice name; generate a write response to the first write request, wherein the write response includes the list of pending write requests; receive, in response to the write response, a finalize request from the first requesting device to finalize storage of the first or the other encoded data slice; and close the list of pending write requests for the slice name.
 16. The computer readable storage device of claim 15, wherein the third memory section further stores operational instructions that, when executed by the storage unit, causes the storage unit to: when the finalize request is regarding the first encoded data slice: delete the other encoded data slice; and update a most current revision level to the new revision level.
 17. The computer readable storage device of claim 16 further comprises: the first write request including a first transaction value; the other write request including a second transaction value; and the third memory section further stores operational instructions that, when executed by the storage unit, causes the storage unit to: determine that the finalize request is regarding the first encoded data slice when the finalize request includes the first transaction value.
 18. The computer readable storage device of claim 16, wherein the third memory section further stores operational instructions that, when executed by the storage unit, causes the storage unit to: delete a previously stored encoded data slice having the slice name and the previous revision level.
 19. The computer readable storage device of claim 15, wherein the third memory section further stores operational instructions that, when executed by the storage unit, causes the storage unit to: when another write request is not pending: open the list of pending write requests to include the first write request; generate a write response to the first write request, wherein the write response includes the list of pending write requests; receive, in response to the write response, a first finalize request to finalize storage of the first encoded data slice; and close the list of pending write requests for the slice name.
 20. The computer readable storage device of claim 19, wherein the third memory section further stores operational instructions that, when executed by the storage unit, causes the storage unit to: determine, prior to receiving the first finalize request, whether the other write request is received; when the other write request is received prior to receiving the first finalize request, update the list of pending write requests to include the other write request; receive, in response to the write response, the finalize request to finalize storage of the first or the other encoded data slice; and close the list of pending write requests for the slice name. 